Molecular pathological analysis of sarcomas using paraffin‐embedded tissue: current limitations and future possibilities

Sarcomas of soft tissue and bone are rare neoplasms that can be separated into a large number of different diagnostic entities. Over the years, a number of diagnostic markers have been developed that aid pathologists in reaching the appropriate diagnoses. Many of these markers are sarcoma‐specific proteins that can be detected by immunohistochemistry in formalin‐fixed, paraffin‐embedded (FFPE) sections. In addition, a wide range of molecular studies have been developed that can detect gene mutations, gene amplifications or chromosomal translocations in FFPE material. Until recently, most sequencing‐based approaches relied on the availability of fresh frozen tissue. However, with the advent of next‐generation sequencing technologies, FFPE material is increasingly being used as a tool to identify novel immunohistochemistry markers, gene mutations, and chromosomal translocations, and to develop diagnostic tests.     

Recently characterized molecular events in uncommon gynaecological neoplasms and their clinical importance

The introduction of new sequencing technologies has resulted in the discovery of commonly mutated genes in uncommon cancers, including non‐epithelial ovarian neoplasms and other rare gynaecological tumours, such as cervical embryonal rhabdomyosarcoma. In some of these neoplasms, mutations in certain genes are both frequent and specific enough for the genomic mutations and sometimes their associated protein loss or overexpression to be used as an aid to diagnosis. In this review, we contrast previous gene identification methods with newer ones, and discuss how the new sequencing technologies (collectively referred to as ‘next‐generation sequencing’) have permitted the identification of specific molecular events that characterize several rare gynaecological neoplasms. We highlight the value of using sequencing to complement traditional pathological methods when diagnosing certain tumours, and provide practical advice to pathologists dealing with these neoplasms. We focus on adult granulosa cell tumours (somatic monoallelic mutations in FOXL2), Sertoli–Leydig cell tumours, gynaecological embryonal rhabdomyosarcomas (germline and somatic mutations in DICER1), and small‐cell carcinoma of the ovary, hypercalcaemic type (biallelic mutations in SMARCA4). The new genetic findings provided by next‐generation sequencing in these uncommon neoplasms have brought these disorders back into focus, and point the way towards new diagnostic, preventive and therapeutic avenues.     

Targeted next‐generation sequencing of cancer genes dissects the molecular profiles of intraductal papillary neoplasms of the pancreas

Intraductal neoplasms are important precursors to invasive pancreatic cancer and provide an opportunity to detect and treat pancreatic neoplasia before an invasive carcinoma develops. The diagnostic evaluation of these lesions is challenging, as diagnostic imaging and cytological sampling do not provide accurate information on lesion classification, the grade of dysplasia or the presence of invasion. Moreover, the molecular driver gene mutations of these precursor lesions have yet to be fully characterized. Fifty‐two intraductal papillary neoplasms, including 48 intraductal papillary mucinous neoplasms (IPMNs) and four intraductal tubulopapillary neoplasms (ITPNs), were subjected to the mutation assessment in 51 cancer‐associated genes, using ion torrent semiconductor‐based next‐generation sequencing. P16 and Smad4 immunohistochemistry was performed on 34 IPMNs and 17 IPMN‐associated carcinomas. At least one somatic mutation was observed in 46/48 (96%) IPMNs; 29 (60%) had multiple gene alterations. GNAS and/or KRAS mutations were found in 44/48 (92%) of IPMNs. GNAS was mutated in 38/48 (79%) IPMNs, KRAS in 24/48 (50%) and these mutations coexisted in 18/48 (37.5%) of IPMNs. RNF43 was the third most commonly mutated gene and was always associated with GNAS and/or KRAS mutations, as were virtually all the low‐frequency mutations found in other genes. Mutations in TP53 and BRAF genes (10% and 6%) were only observed in high‐grade IPMNs. P16 was lost in 7/34 IPMNs and 9/17 IPMN‐associated carcinomas; Smad4 was lost in 1/34 IPMNs and 5/17 IPMN‐associated carcinomas. In contrast to IPMNs, only one of four ITPNs had detectable driver gene (GNAS and NRAS) mutations. Deep sequencing DNA from seven cyst fluid aspirates identified 10 of the 13 mutations detected in their associated IPMN. Using next‐generation sequencing to detect cyst fluid mutations has the potential to improve the diagnostic and prognostic stratification of pancreatic cystic neoplasms. © 2014 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.     

Massive parallel sequencing of solid tumours – challenges and opportunities for pathologists

The role of pathologists is to provide diagnostic, prognostic and predictive data to enable clinical colleagues to manage patients optimally. Current histo/anatomical pathology is predominantly morphology‐based, with the addition of biomarkers, applied largely through immunohistochemistry, fluorescence in‐situ hybridization (FISH) and a limited range of polymerase chain reaction (PCR)‐based molecular tests. The desire to apply genomics to the clinical care of patients has been facilitated by the human genome project and subsequently by high‐throughput technologies known collectively as massive parallel sequencing (MPS, also referred to as next‐generation sequencing, NGS). The use of MPS to identify mutations/variants and tissue RNA expression profiles for diagnosis, prognostication and targeted therapy stratification is now a reality in many clinical specialities. If histopathologists are considered experts in solid tumour pathology, MPS potentially falls within their scope; however, it challenges our predominant morphology‐based paradigm. This review summarizes and comments on the current and future state of play of MPS for the practising histopathologist. It will focus on somatic mutations in solid tumours and will challenge histopathologists to take further leadership roles in this area.     

Integrating next‐generation sequencing into the diagnostic testing of inherited cancer predisposition

The clinical application of next‐generation sequencing (NGS) as a diagnostic tool has become increasingly evident. The coupling of NGS technologies with new genomic sequence enrichment methods has made the sequencing of panels of target genes technically feasible, at the same time as making such an approach cost‐effective for diagnostic applications. In this article, we discuss recent studies that have applied NGS in the diagnostic setting in relation to hereditary cancer.     

Targeted Next‐Generation Sequencing can Replace Sanger Sequencing in Clinical Diagnostics

Mutation detection through exome sequencing allows simultaneous analysis of all coding sequences of genes. However, it cannot yet replace Sanger sequencing (SS) in diagnostics because of incomplete representation and coverage of exons leading to missing clinically relevant mutations. Targeted next‐generation sequencing (NGS), in which a selected fraction of genes is sequenced, may circumvent these shortcomings. We aimed to determine whether the sensitivity and specificity of targeted NGS is equal to those of SS. We constructed a targeted enrichment kit that includes 48 genes associated with hereditary cardiomyopathies. In total, 84 individuals with cardiomyopathies were sequenced using 151 bp paired‐end reads on an Illumina MiSeq sequencer. The reproducibility was tested by repeating the entire procedure for five patients. The coverage of ≥30 reads per nucleotide, our major quality criterion, was 99% and in total ～21,000 variants were identified. Confirmation with SS was performed for 168 variants (155 substitutions, 13 indels). All were confirmed, including a deletion of 18 bp and an insertion of 6 bp. The reproducibility was nearly 100%. We demonstrate that targeted NGS of a disease‐specific subset of genes is equal to the quality of SS and it can therefore be reliably implemented as a stand‐alone diagnostic test.     

Targeted deep sequencing of effusion cytology samples is feasible,informs spatiotemporal tumor evolution,and has clinical and diagnostic utility

During the course of disease, many cancer patients eventually present with metastatic disease including peritoneal or pleural spread. In this context, cytology specimens derived from ascites or pleural effusion may help to differentiate malignant from benign conditions and sometimes yield diagnosis of a malignancy. However, even when supported by immunohistochemistry, cytological interpretation can be challenging, especially if tumor cellularity is low. Here, we investigated whether targeted deep sequencing of formalin‐fixed and paraffin embedded (FFPE) cytology specimens of cancer patients is feasible, and has diagnostic and clinical impact. To this end, a cohort of 20 matched pairs was compiled, each comprising a cytology sample (FFPE cell block) and at least one biopsy/surgical resection specimen serving as benchmark. In addition, 5 non‐malignant effusions were sequenced serving as negative‐controls. All samples yielded sufficient libraries and were successfully subjected to targeted sequencing employing a semiconductor based next‐generation sequencing platform. Using gene panels of different size and composition, including the Oncomine Comprehensive Assay, for targeted sequencing, somatic mutations were detected in the tissue of all 20 cases. Of these, 15 (75%) harbored mutations that were also detected in the corresponding cytology samples. In four of these cases (20%), additional private mutations were detected in either cytology or tissue samples, reflecting spatiotemporal tumor evolution. Of the five remaining cases, three (15%) showed wild type alleles in cytology material whereas tumor tissue had mutations in interrogated genes. Two cases were discordant, showing different private mutations in the cytology and in the tissue sample, respectively. In summary, sequencing of cytology specimens (FFPE cell block) reflecting spatiotemporal tumor evolution is feasible and yields adjunct genetic information that may be exploitable for diagnostics and therapy.     

CIC‐NUTM1 fusion: A case which expands the spectrum of NUT‐rearranged epithelioid malignancies

NUT carcinoma (NC) shows very aggressive clinical behavior, occurs predominantly in the thorax and head and neck region of children and adults, and is defined by the presence of NUT (aka NUTM1) rearrangement, mostly BRD4‐NUTM1 fusion resulting from t(15;19)(q13; p13.1). So‐called “NUT variants” harbor alternate fusions between NUTM1 and BRD3, NSD3, ZNF532, or unknown partners. Rare cases of pediatric tumors with CIC‐NUTM1 fusion were recently reported in somatic soft tissue, brain, and kidney. However, such cases have not been identified in adult patients and the presence of a fusion between CIC, characteristic of CIC‐rearranged sarcoma, and NUTM1—a defining feature of NC—poses a diagnostic challenge. We herein report a case of malignant epithelioid neoplasm with myoepithelial features harboring CIC‐NUTM1 fusion arising in soft tissue of the head in a 60‐year‐old man. Immunohistochemistry revealed strong expression of NUT, but only weak ETV4 staining and negativity for keratins, EMA, p40, CD99, and WT1. SMARCB1 expression was retained. Fluorescence in situ hybridization and targeted next‐generation sequencing identified a CIC‐NUTM1 fusion resulting from t(15;19)(q14;q13.2). In light of morphologic features that overlap with those of NC from typical anatomical sites we have seen previously, the tumor was best classified as falling within the NC spectrum rather than CIC‐associated sarcoma. This case highlights the emerging diagnostic challenges generated by newly detected gene fusions of unknown clinical and biologic significance. Careful integration of cytogenetic, molecular, and immunohistochemical findings with morphologic appearances in the diagnostic workup of undifferentiated neoplasms is essential.     

Muscular dystrophies and myopathies: the spectrum of mutated genes in the Czech Republic

Inherited neuromuscular disorder (NMD) is a wide term covering different genetic disorders affecting muscles, nerves, and neuromuscular junctions. Genetic and clinical heterogeneity is the main drawback in a routine gene‐by‐gene diagnostics. We present Czech NMD patients with a genetic cause identified using targeted next‐generation sequencing (NGS) and the spectrum of these causes. Overall 167 unrelated patients presenting NMD falling into categories of muscular dystrophies, congenital muscular dystrophies, congenital myopathies, distal myopathies, and other myopathies were tested by targeted NGS of 42 known NMD‐related genes. Pathogenic or probably pathogenic sequence changes were identified in 79 patients (47.3%). In total, 37 novel and 51 known disease‐causing variants were detected in 23 genes. In addition, variants of uncertain significance were suspected in 7 cases (4.2%), and in 81 cases (48.5%) sequence changes associated with NMD were not found. Our results strongly indicate that for molecular diagnostics of heterogeneous disorders such as NMDs, targeted panel testing has a high‐clinical yield and should therefore be the preferred first‐tier approach. Further, we show that in the genetic diagnostic practice of NMDs, it is necessary to take into account different types of inheritance including the occurrence of an autosomal recessive disorder in two generations of one family.     

Next generation sequencing of the cellular and liquid fraction of pancreatic cyst fluid supports discrimination of IPMN from pseudocysts and reveals cases with multiple mutated driver clones: First findings from the prospective ZYSTEUS biomarker study

Approximately half of all pancreatic cysts are neoplastic, mainly comprising intraductal papillary mucinous neoplasms (IPMN), which can progress to invasive carcinoma. Current Fukuoka guidelines have limited sensitivity and specificity in predicting progression of asymptomatic pancreatic cysts. We present first results of the prospective ZYSTEUS biomarker study investigating (i) whether detection of driver mutations in IPMN by liquid biopsy is technically feasible, (ii) which compartment of IPMN is most suitable for analysis, and (iii) implications for clinical diagnostics. Twenty‐two patients with clinical inclusion criteria were enrolled in ZYSTEUS. Fifteen cases underwent endoscopic ultrasound (EUS)‐guided fine‐needle aspiration and cytological diagnostics. Cellular and liquid fraction of the cysts of each case were separated and subjected to deep targeted next generation sequencing (NGS). Clinical parameters, imaging findings (EUS and MRI), and follow‐up data were collected continuously. All IPMN cases (n = 12) showed at least one mutation in either KRAS (n = 11) or GNAS (n = 4). Three cases showed both KRAS and GNAS mutations. Six cases harbored multiple KRAS/GNAS mutations. In the three cases with pseudocysts, no KRAS or GNAS mutations were detected. DNA yields were higher and showed higher mutation diversity in the cellular fraction. In conclusion, mutation detection in pancreatic cyst fluid is technically feasible with more robust results in the cellular than in the liquid fraction. Current results suggest that, together with imaging, targeted sequencing supports discrimination of IPMN from pseudocysts. The prospective design of ZYSTEUS will provide insight into diagnostic value of NGS in preoperative risk stratification. Our data provide evidence for an oligoclonal nature of IPMN.     

Somatic mutations of DICER1 and KMT2D are frequent in intraocular medulloepitheliomas

Intraocular medulloepithelioma (IO‐MEPL) is an uncommon embryonal neuroepithelial neoplasm of the eye. Little is known about the cytogenetics, molecular biology, and pathogenesis of this tumor. In the present study we investigated the mutational landscape of 19 IO‐MEPL using targeted next‐generation sequencing. Routinely prepared paraffin‐embedded samples were assessed with high‐coverage genome sequencing on the Illumina NextSeq 500 platform using a customized gene panel set covering the coding region of 130 genes. This revealed several notable genomic alterations, including mutations of DICER1 (6 tumors) and KMT2D (also known as MLL2; 5 tumors)—which are frequently recurrent and mutually exclusive molecular events for IO‐MEPL. Non‐recurrent mutations in the cancer‐associated genes BRCA2, BRCA1, NOTCH2, CDH1, and GSE1 were also identified. IO‐MEPL samples harboring a DICER1 mutation disclosed few chromosomal alterations and formed a separate DNA methylation cluster, indicating potential differences in genetic and epigenetic events arising perhaps from the presence of this aberration in the tumor genome. The high proportion of recurrent somatic DICER1 and KMT2D mutations in this series of sporadic IO‐MEPL points to their likely important roles in the molecular pathogenesis of these rare embryonal tumors, and perhaps suggests the existence of distinct molecular variants of IO‐MEPL. Although the precise role of these recurrent mutations in the development of IO‐MEPL, and their relationship to pro‐oncogenic molecular mechanisms, have yet to be determined, unraveling their roles could eventually be exploited for nonsurgical therapies of these neoplasms. © 2016 Wiley Periodicals, Inc.     

Detailed analysis of HTT repeat elements in human blood using targeted amplification‐free long‐read sequencing

Amplification of DNA is required as a mandatory step during library preparation in most targeted sequencing protocols. This can be a critical limitation when targeting regions that are highly repetitive or with extreme guanine–cytosine (GC) content, including repeat expansions associated with human disease. Here, we used an amplification‐free protocol for targeted enrichment utilizing the CRISPR/Cas9 system (No‐Amp Targeted sequencing) in combination with single molecule, real‐time (SMRT) sequencing for studying repeat elements in the huntingtin (HTT) gene, where an expanded CAG repeat is causative for Huntington disease. We also developed a robust data analysis pipeline for repeat element analysis that is independent of alignment of reads to a reference genome. The method was applied to 11 diagnostic blood samples, and for all 22 alleles the resulting CAG repeat count agreed with previous results based on fragment analysis. The amplification‐free protocol also allowed for studying somatic variability of repeat elements in our samples, without the interference of PCR stutter. In summary, with No‐Amp Targeted sequencing in combination with our analysis pipeline, we could accurately study repeat elements that are difficult to investigate using PCR‐based methods.     

Cytologic diagnosis of osseous lesions: A review with emphasis on the diagnosis of primary neoplasms of bone

Fine‐needle aspiration has been utilized as the initial diagnostic technique at a large number of body sites for over three quarters of a century. As early as the 1930s, fine‐needle aspiration (FNA) was used to investigate lesions of the musculoskeletal system. In many early reports, FNA was most frequently and successfully used for the diagnosis of metastatic disease to bone. Less emphasis was placed on its utility for the investigation of primary neoplasms of bone and soft tissue. Current utilization of FNA continues to de‐emphasize its application to the diagnosis of primary lesions of the musculoskeletal system. Recent advances in imaging techniques, immunohistochemistry, and molecular diagnostics along with an increasing familiarity among pathologists with the cytologic appearance of primary osseous tumors has led to reevaluation of the technique for investigation of these tumors. The diagnostic accuracy of FNA along with its relatively low cost and high degree of safety makes it a desirable technique for the investigation of primary lesions of the musculoskeletal system. This article reviews issues of diagnostic accuracy, optimal practice procedures, and benefits of the technique including cost reduction. The article will review criteria for selection of appropriate tissue targets for FNA to reduce the number of unsatisfactory specimens. Cytomorphologic features of the more common primary neoplasms of bone will be summarized along with recommendations for the utilization of immunohistochemistry and molecular diagnostics in the work‐up of primary neoplasms of bone. Diagn. Cytopathol. 2009. © 2009 Wiley‐Liss, Inc.     

Results of next‐generation sequencing gene panel diagnostics including copy‐number variation analysis in 810 patients suspected of heritable thoracic aortic disorders

Simultaneous analysis of multiple genes using next‐generation sequencing (NGS) technology has become widely available. Copy‐number variations (CNVs) in disease‐associated genes have emerged as a cause for several hereditary disorders. CNVs are, however, not routinely detected using NGS analysis. The aim of this study was to assess the diagnostic yield and the prevalence of CNVs using our panel of Hereditary Thoracic Aortic Disease (H‐TAD)‐associated genes. Eight hundred ten patients suspected of H‐TAD were analyzed by targeted NGS analysis of 21 H‐TAD associated genes. In addition, the eXome hidden Markov model (XHMM; an algorithm to identify CNVs in targeted NGS data) was used to detect CNVs in these genes. A pathogenic or likely pathogenic variant was found in 66 of 810 patients (8.1%). Of these 66 pathogenic or likely pathogenic variants, six (9.1%) were CNVs not detectable by routine NGS analysis. These CNVs were four intragenic (multi‐)exon deletions in MYLK, TGFB2, SMAD3, and PRKG1, respectively. In addition, a large duplication including NOTCH1 and a large deletion encompassing SCARF2 were detected. As confirmed by additional analyses, both CNVs indicated larger chromosomal abnormalities, which could explain the phenotype in both patients. Given the clinical relevance of the identification of a genetic cause, CNV analysis using a method such as XHMM should be incorporated into the clinical diagnostic care for H‐TAD patients.     

Lake Louise Mutation Detection Meeting 2013: Clinical Translation of Next‐Generation Sequencing Requires Optimization of Workflows and Interpretation of Variants

With the exponential reduction of the cost of next‐generation sequencing (NGS), it is no longer the generation of data but the analysis and interpretation of massive amounts of sequencing data that are seen as key challenges for the effective integration of these technologies into clinical practice. Clinical geneticists, informaticians, and scientists from 17 countries gathered for the 12th International Symposium on Mutation in the Genome at the Fairmont Chateau Lake Louise (Canada) to discuss technological advances and applications of NGS and consider possible approaches to the challenges of clinical translation. Here, we provide an overview of the main themes of the meeting that included development of innovative solutions for variant sharing, tools and resources for NGS analysis, novel technology and methodology development, NGS‐based discovery of disease pathogenesis, development of multigene NGS sequencing panels for clinical use, exploring diagnostic utility of whole‐exome and whole‐genome sequencing, and, finally, integration of genomic sequencing into the clinic.     

Clinical Applications of Next‐Generation Sequencing: The 2013 Human Genome Variation Society Scientific Meeting

Next‐generation sequencing (NGS) has significantly contributed to the transformation of genomic research by providing access to the genome for analysis, by significantly decreasing the sequencing costs and increasing the throughput. The next goal is to exploit this powerful technology in the clinic, namely for diagnostics and therapeutics. The 2013 annual meeting of the Human Genome Variation Society, held in Paris, France, provided a forum to discuss possible clinical applications of NGS, the potential of some of the current NGS systems to transition to the clinic, the identification of causative mutations for rare genetic disorders through whole‐genome or targeted genome resequencing, the application of NGS for family genomics, and NGS data analysis tools.     

Informed consent for exome sequencing in diagnostics: exploring first experiences and views of professionals and patients

Next‐generation sequencing is increasingly being chosen as a diagnostic tool for cases of expected genetic, but unresolved origin. The consequential increased need for decisions on disclosure of unsolicited findings poses a challenge for the informed consent procedure. This study explored the first experiences with, and needs for, the informed consent procedure in diagnostic exome sequencing, with the stakeholders involved. Semi‐structured interviews were conducted with 11 professional experts and one professional gave a written response. Furthermore, the counseling process was observed in three cases where exome sequencing was offered, followed by interviews with the patient (representative) and the genetic counselor. The respondents not only preferred an opt‐out for unsolicited findings but also identified many challenges and therefore more experiences with exome sequencing was considered needed. Context‐dependent decision‐making was observed and an Advisory Board for unsolicited findings was considered helpful while doubts were raised about the feasibility and the possibility of undermining patients' autonomy. Finally, respondents brought up the complexity of information provision, and division of responsibilities between clinicians and the lab. These challenges and needs, raised by stakeholders involved, provide more insight in the next steps needed for an optimal informed consent procedure for exome sequencing in diagnostics.